^1,2Zachary F.M. Burton,^2,3Janice L. Bishop,⁴Peter A.J. Englert,⁵Anna Szynkiewicz,⁶Christian Koeberl,⁴Przemyslaw Dera,⁴Warren McKenzie,⁷Everett K. Gibson
American Mineralogist 108, 1017-1031 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1017.pdf]
¹Department of Earth and Planetary Sciences, Stanford University, Stanford, California 94305, U.S.A.
²Carl Sagan Center, The SETI Institute, Mountain View, California 94043, U.S.A.
³NASA Ames Research Center, Moffett Field, California 94035, U.S.A.
⁴Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, Hawaii 96822, U.S.A.
⁵Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996, U.S.A.
⁶Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria 7
NASA Johnson Space Center, Houston, Texas 77058, U.S.A
Copyright: The Mineralogical Society of America

Understanding past and present aqueous activity on Mars is critical to constraining martian aqueous
geochemistry and habitability, and to searching for life on Mars. Assemblages of minerals observed
at or near the martian surface include phyllosilicates, sulfates, iron oxides/hydroxides, and chlorides,
all of which are indicative of a complex history of aqueous activity and alteration in the martian past.
Furthermore, features observed on parts of the martian surface suggest present-day activity of subsurface
brines and at least transient liquid water. Terrestrial analogs for younger and colder (Hesperian–Amazonian) martian geologic and climatic conditions are available in the McMurdo Dry Valleys (MDV)
of Antarctica and provide opportunities for improved understanding of more recent aqueous activity
on Mars. Here, we study the VXE-6 intermittent brine pond site from Wright Valley in the MDV
region and use coordinated spectroscopy, X-ray diffraction, and elemental analyses to characterize
the mineralogy and chemistry of surface sediments that have evolved in response to aqueous activity
at this site. We find that brine pond activity results in mineral assemblages akin to aqueous alteration
products associated with younger sites on Mars. In particular, surficial chlorides, a transition layer
of poorly crystalline aluminosilicates and iron oxides/hydroxides, and a deeper gypsum-rich interval
within the upper 10 cm of sediment are closely related at this Antarctic brine pond site. Activity of the
Antarctic brine pond and associated mineral formation presents a process analog for chemical alteration on the martian surface during episodes of transient liquid water activity during the late Hesperian
and/or more recently. Our results provide a relevant example of how aqueous activity in a cold and
dry Mars-like climate may explain the co-occurrence of chlorides, clays, iron oxides/hydroxides, and
sulfates observed on Mars.